This invention concerns connectors for making electrical connections, particularly temporarily, to an electrical device, and, more particularly, to test clip type connectors for making connections to peripherally extending leads of surface mount chip carriers that are installed in sockets mounted on a printed circuit board.
Many test clips and connectors for making electrical connections to leads extending from an integrated circuit package are known. An example of a test clip for an integrated circuit of the dual-in-line (DIP) package type, is disclosed in U.S. Pat. No. Re. 28,064. DIP packages may have from 14 to 64 leads arranged in a pair of parallel rows on the two generally relatively longer parallel sides of the DIP package. Typically the leads are spaced on 0.100 inch (2.5 mm.) centers. The DIP package may be installed by inserting the leads into a DIP socket that has been soldered to a printed circuit board. DIP packages are oridinarily spaced from each other and from other components on a printed circuit board by distances of at least several tenths of an inch. The reissue patent test clip may be used to make electrical connections with each of the leads of a DIP package for signal testing and signal injecting purposes while the integrated circuit package is in its usual mounting or when it is unmounted.
More recently, integrated circuit packages have been developed that permit denser packing of integrated circuits on printed circuit boards. These packages also have a greater number of leads since they are used with more complex integrated circuits. These types of packages are referred to as LCC's for leaded chip carriers. LCC's typically can accommodate one or more circuit chips that are mounted on a lead frame. The lead frame connections are electrically and mechanically connected to the LCC leads. The LCC is completed by encasing the chip or chips with an electrically non-conductive encapsulating medium. Exemplary encapsulating media include plastic or plastic-like material or ceramic material. In the case that plastic material is used, the designation PLCC, for plastic leaded chip carrier, is sometimes used. As compared to DIP's, LCC's can be far more densely packed on a printed circuit board. This improvement is attributable at least in part to location of leads along all sides of an LCC and narrowed spacing between leads in an LCC. LCC's can be mounted close to each other on a printed circuit board, for example, 0.035 inch (0.88 mm.) apart.
State-of-the-art LCC's are generally square or rectangular and may have a large number of leads, e.g., 132 leads, 33 leads per side, extending from a square package. Other packages may have a total of 20 or more leads. In a typical 20 lead LCC, the leads are positioned on 0.050 inch (1.27 mm.) centers along each side. Obviously as the density of packing increases, the size of leads decreases. Various arrangements of leads for surface mounting LCC packages have been devised. Some LCC packages use leads that are bent in semicircles to extend under the LCC package. These packages may be positioned on a printed circuit board with the leads touching prepared solder lands. The solder is melted long enough to establish mechanical and electrical connection between the respective LCC leads and lands. Alternatively, the LCC may be inserted into a socket that is soldered to a printed circuit board. The socket includes a separate contact for establishing an electrical connection from each of the LCC leads to a soldered connection on the printed circuit board.
It is desirable to have a test probe to make temporary electrical connections with each of the leads of an LC or DIP mounted in a socket for signal sensing or signal injection. Preferably, the test probe leads make a connection to each of the leads of an LCC or DIP that is electrically and mechanically stable, self-retaining and can be disconnected when desired without disturbing the socketed LCC or DIP. The close spacing of the LCC and DIP leads means that the test probe contacts must be small and that they are therefore delicate. A test connector should protect these delicate probe leads against bending or other damage and should control the probe leads' positions to avoid short circuiting between the LCC or DIP leads being probed.
Accordingly, it would be desirable to provide a connector for contacting an LCC or DIP mounted in a socket and disposed on a densely packed printed circuit board. It would be particularly desirable to provide such a connector that can make a separate, self-retaining, disconnectable electrical and mechanical contact to the LCC or DIP leads that can be disconnected without disturbing the socketed LCC or DIP.